1. Field of the Invention
The present invention relates to a light-receiving element having a control electrode and a display device including such a light-receiving element.
2. Description of Related Art
In recent years, for display devices such as a liquid crystal display device and an organic EL display device, a light-receiving element such as a photodiode is being widely used in order to detect and control the brightness and the contrast of a displayed image. The photodiode is incorporated in the display device together with a display element having a drive circuit composed of a thin film transistor (TFT) and so on.
As one kind of such a photodiode, a PIN photodiode having a planar shape is known. The PIN photodiode includes a p-type semiconductor region and an n-type semiconductor region that are formed over a transparent substrate surface and are composed of polycrystalline silicon, and an i-type semiconductor (intermediate semiconductor) region therebetween, formed over the transparent substrate surface and composed of polycrystalline silicon.
In Japanese Patent Laid-open No. 2004-119719, for example, a technique of controlling the threshold voltage by using a third electrode (gate electrode) for the PIN photodiode has been proposed.